1. Field of the Invention
The invention relates to mobile, road-hauled aggregate material processing plant such as screening plant, crushing plant for quarries, or mining plant. Examples of such plant are described in U.S. Pat. Nos. 4,237,000 (Read) and 4,256,572 (Read). In this specification, the term "aggregate material" means materials such as sand, crushed stones, bricks and any construction material, loam, mined material such as coal, or recyclable materials, timber, wood chips etc.
2. Prior Art Discussion
In an aggregate material processing plant generally, processing capacity is heavily influenced by the ability to quickly and effectively deliver the processed material away from the plant. To achieve this, it is known to provide lateral conveyors which extend transversely of the plant, possibly in addition to longitudinal conveyors. While the manner in which such lateral conveyors are connected to the plant is relatively simple for the operative position, where the processing plant is mobile major problems arise in ensuring that the overall width and height of the mobile plant is within certain dimensions when carrying such conveyors during transport. Another problem is ensuring safety, on-site, in movement of the lateral conveyors to a position for transport of the mobile plant. A still further problem is that of providing for easy and safe maintenance or repair of the lateral conveyors on-site or at a workshop.
In British Patent Specification No. GB-2223963 (J. McDonald) an arrangement is described whereby conveyors including a lateral conveyor are separated from the mobile plant and are then lifted by a loader onto upper support brackets mounted above the plant. These brackets significantly increase the height of the plant. Further, carrying separated conveyor sections on such brackets may be a safety hazard. It is a time-consuming and awkward exercise to separate the conveyor sections, mount them on a loader and lift them onto the brackets.
PCT Patent Specification No. WO 85/03652 (Powerscreen Int. Ltd.) describes a mobile screening apparatus in which there is a pair of opposed lateral conveyors extending on opposite sides of the apparatus. The conveyors are mounted on pivots which allow them to be pivoted from a laterally-extending operative position at 24.degree. to horizontal to a transport position extending longitudinally at 10.degree.-12.degree. to the horizontal. Because the plant must accommodate the conveyors in the transport position in this manner, it must be of sufficient length to avoid a situation where they protect longitudinally beyond the plant. Another problem is that plant equipment mounted on the chassis must be narrow enough along the full length of the lateral conveyors so that they do not extend laterally. This aspect puts considerable design limitations on the plant, which may affect its processing capacity. For repair or maintenance of the lateral conveyors, access by personnel may be difficult and unsafe in some situations.
British Patent Specification No. GB 1,480,688 (Machines & Structures Ltd.) also describes a mobile screening plant having lateral conveyors. These conveyors are pivotable about a vertical axis through 180.degree. for delivery of separated material to different stockpiles. The range of rotation appears to include a transport position at which they lie longitudinally alongside the processing plant. Accordingly, similar problems appear to arise as for the machine described in Specification No. WO 85/03652.
In British Patent Specification No. GB 1,449,001 (Powerscreen Int. Ltd.) a mobile separating apparatus is described which has a pair of lateral conveyors. Cross-reference is made to conveyor arrangements described in GB 1,414,786 and GB 1,415,640 (Powerscreen Int. Ltd.). In these specifications, conveyors are described which rotate about a vertical pivot axis between longitudinal and lateral positions. It appears that the longitudinal positions are used for transport, thus extending the length of the plant.
Thus, while lateral conveyors have been extensively used in the past and there have been many solutions to the problems, there are still many practical problems which arise for transport of the mobile plant. These problems can be very important where the plant is frequently moved from site to site and where the plant must be transported over large distances from the place of manufacture.